•Distributed
systems are very hard
–A distributed system is one in which I can't get my
work done because
a computer I've never heard of has failed. Butler Lampson
•When
building distributed systems, we often observe unexpectedly low performance
•the
reasons for which are usually not obvious
•The
bottlenecks can be in any of the following components:
–the
applications
–the
operating systems
–the
disks, network adapters, bus, memory, etc. on either the sending or receiving host
–the
network switches and routers, and so on
•Problems
may not be logical
–Most
problems are operator errors, configurations, bugs